Synlett 2006(17): 2683-2698  
DOI: 10.1055/s-2006-950280
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© Georg Thieme Verlag Stuttgart · New York

Doubly Charged Four-Membered Ring Systems: Cyclobutadiene Dianions and Heavy Cyclobutadiene Dianions

Akira Sekiguchi*a, Tsukasa Matsuob
a Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
Fax: +81(298)534314; e-Mail: sekiguch@staff.chem.tsukuba.ac.jp;
b Coordination Chemistry Laboratories, Institute for Molecular Science, Okazaki, Aichi, 444-8787, Japan
Fax: +81(564)595589; e-Mail: tmatsu@ims.ac.jp;
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Publikationsverlauf

Received 13 February 2006
Publikationsdatum:
09. Oktober 2006 (online)

Abstract

Recent progress in the experimental chemistry of cyclo­butadiene dianions (CBD2-s) containing a doubly charged four-membered ring system is reviewed. New families of silyl-substituted CBD2-s, cyclobutadienes (CBDs), and tetrahedranes are covered in detail. The aromaticity of the tetrasilyl- and diphenyldisilyl-CBD2-s have been studied on the basis of structural characteristics and magnetic properties. All of the CBD2-s show a strong diatropic ring current resulting from six π-electron system. The preparation of CBD2- derivatives consisting of heavier group 14 elements (Si and Ge) is also included. They demonstrate a non-aromatic nature with a folded four-membered ring.

  • 1 Introduction

  • 2 Cyclobutadiene Dianions (CBD2-s)

  • 2.1 Preparation of CBD Complexes

  • 2.2 Transmetalation of CBD Complexes

  • 2.3 Tetrasilyl-CBD2-s

  • 2.4 Diphenyl-Disilyl-CBD2-s

  • 3 Cyclobutadienes (CBDs)

  • 4 Tetrahedranes

  • 5 Heavy Cyclobutadiene Dianions (CBD2-s)

  • 6 Conclusion

3

A thematic issue of aromaticity, edited by von Ragué Schleyer, P., has been published: Chem. Rev. 2001, 101, 1115-1566.

36

Tanaka, M.; Sekiguchi, A. unpublished results.